Commonly, portable cellular radio telephones are provided with removable batteries as their current source. Typically, these batteries are rechargeable Nickel-Cadmium (Ni--Cd) batteries.
To recharge the battery, the battery is left attached to the cellular radio telephone and is recharged in situ by means of a charging unit. In use, the charging unit is coupled to a mains alternating current supply via a conventional plug arrangement, for example, in the United Kingdom this is a conventional 3-pin plug arrangement well known to persons skilled in the art. The charging unit is coupled to the rechargeable battery by means of a multi-conductor cable which terminates, at its free end, in an electrical connector which is arranged to contact matching contacts on the telephone. The charging unit, typically, may be a simple transformer/current generator or switch mode supply. Such charging units are well known to persons skilled in the art. In use, the charging unit is plugged into the mains supply using the plug provided on the unit and the pin is plugged into the telephone. The rechargeable battery is left plugged into the charging unit until the battery is recharged.
The portable appliance charging units are usually supplied with the plug arrangement for the country in which the charging unit is sold. However, as is well known, different regions of the globe have adopted different mains plug and socket arrangements. For example, the United Kingdom, continental Europe, the USA, and Australia all have different arrangements. This is, of course, extremely inconvenient for the traveller, who must purchase an adapter to allow the unit to be used in the country to which that person is travelling. These adapters commonly do not always provide continuous coupling between the mains supply and the unit because the pins are held loosely in the adapter, which can lead to incomplete recharging--particularly so, when the device is left unattended.
A known power supply unit is supplied with a number of interchangeable plug adapter units, each with a different arrangement of pins. The plug adapter unit with the correct pin arrangement for use in a particular region is selected and then clipped onto the power supply unit to allow it to be plugged into the mains.